Method and apparatus for manufacturing abrasive materials



E. HuRsT 2,369,462

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METHOD AND APPARATUS FOR MANUFACTURING ABRAsIvE MATERIALS @NQQ l|1 A. N. @l

ATTORNEY..

Feb. 13, 14945. E. HuRsT 2,369,452 METHOD AND" APPARATUS FOR MANUFACTURING ABRASVE WINTERT ALJSr Filed Jan. 22, 1941 l( '2 Sheets-Sheet- 42 a al y INVENTOR. EDWA RD HL] RST ATTGRNEY.

vpt itented v 13,

`.UNITED STATES PATENT ori-fica METHOD AND APPARATUS FOR MANUFAC- TUBING ABRASIVE MATERIALS Edward Hurst, West-Newton, Mass., asslgnor to United Cotton Produets'Company, Fall River, v Mass., a corporation of Massachusetts Application January 22, 1941, Serial No. 375,517

terial and-to methods and apparatus for manuy facture thereof. More particularly, the present invention is concerned with the manufacture of abrasive materials in which the fibers of a. plurality of carded fibrous membranes are formed together'` by denite interengagement or interweaving to form a substantially non-lamellar web structure and abrasive grain included internally of the web and/or extending in partjabove' the surface thereof. This invention is` concer1`1ed further with the manner of introducing or including the Wabrasive material andan adhesive binder Iagent into the web so that the abrasive particles are anchored in the interstices of they fibers and the gussets"made by the fiber inter- 'sections'and further cemented in place by the of the backing and the distinctline of demarcation `which has existed heretofore between the backing member and the coating of abrasive granules. In addition, its brous structure lends a strength, controllable flexibility and durability to the final product which meets the requirements for abrasive palper, as well as many appli- 12 ciaims. (ci. 51-297) This invention relates to webs of abrasive maa strong non-lamellar web structure and apply ing abrasive granular material internally of .said fibrous web,` said abrasive particles extending 'from the interior to the surface and projecting' therefrom. A suitablel adhesive agent is also incorporated vwithin said web and the treated A`fibrous web is consolidated to a desired density..

The present invention iurthe1 'provides a method and suitable apparatus with which the abrasive grain and the adhesivebinder maybe applied to the web and caused to' penetrate and permeate throughout the fibrous web structure.

" The abrasive `particles enter into ,theV interstices cations for which the conventional abrasive Paper is not suited.

- Methods have been proposed for the incorporation of abrasive grain vinto a paper base by mixing abrasive grains into 'a macerated, watery mass' of paper pulp and then forming abrasive articles from the mixture; Such methods have been unsatisfactory because of the fact that a solid,

densely-matted body was formed which entirely masked the cutting edges of the abrasive particles, and also the absence of clearance spaces prevented the formation of chips.

I have found that the above difficulties can be overcome and fiexi'ble abrasive .web materialsV produced with a substantial saving in time and operations by forming a web of a plurality of carded fibrous membranes, forming said memhranes together by definite interweaving lto form terial or to the o f the individual fibers and between the 'fibers 4of the web, and when the web is consolidated, the individual bers are pressed down and around the base of each individual abrasive particle to increase the anchorage thereof. 'This also `causes the cutting edges of the uppermost grains to project above the surface of the web and a sharp abrading surface is produced. Furthermore, the mabrading action is `not confined to a superimposed 'layer of abrasive `grains onthe upper surface of the web, but the abrasive properties extend substantially all the waythrough said web, there being no distinct linevof demarcation between the fibrous web and the'abrading surface. V j v Abrasive grain can 'be introduced entirely-or partially within the fibrous web structure in amount and character to suit the conditions and nature of theintended use. For example, the abrasive grainfmay be applied in such a manner that there is a maximum amount of abrasive particles at one surface of the web, withV the amount of grain progressively diminishing as the distancefrcm thatsurface 'of the web becomes vgreater, there being little or no abrasive grain at theopposing surface of the web. However, if desired, the abrasive may be applied into both surfaces ofthe web and an article produced in which the Aquantity of grain diminishes equally lfrom both surfaces of the weli toward the interior.

A coating'of abrasive grain may also be applied, if

desired, and adhesively secured tothe top surface of the web. A sizing layer of adhesive may be applied to the surface coating of abrasive masurface of the abrasive-included web. y v

Various modifying agents, such as waterproofing compounds, anti-friction agents, embrittling materials, iiexibilizers and other fillers, may be incorporated in the web during manufacturelin order to render the web resistant to water orimpart specific properties thereto.

' In order'that the invention may be more clearly set forth and made more understandable, reference is made to the accompanying drawings, in which Figure 1 is a diagrammatic vside elevation of one form of apparatus for making abrasive webs in accordance with the present invention;

Figure 2 is an enlarged view of a portion of the apparatus of Figure 1, and shows the adhesiveapplying means in greater detail, as well as modifled means for. applying the abrasive grain into and through the web; l

Figure 3 is a modification of the apparatus shown in Figure 2; f Figure 4 is aygreatly enlarged vertical-section through a fragment of an abrasive web made according to the present invention; and Figure 5 is a similarly enlarged vertical-section 4 of a modified fo'rm of web made in accordance with the present invention.

Figure 1 of the drawings illustrates one form of apparatus which may be employed in the production of fibrous abrasive materials by the concurrent manufacture of a fibrous web material and the inclusion of abrasive grains and adhesive binder therein. Y The particular apparatus shown includes a plurality of card assemblies suitably spaced apart and consisting of card cylinders 2, doier cylinders 3 and combs 4 adapted to form and deliver a number of carded membranes 5, 6, 'I and 8 vto the moving conveyor II. The carded membranes are uniform webs of loosely adhering independent fibers and may consist of any animal, vegetable, mineral or synthetic fibrous material capable of being carded into web form. Such materials include natural fibers, such as cotton, wool, jute, fiax and the like, or any of the newer synthetic fibers, such as glass wool', resinous or synthetic'rubber-like fibrous materials. Any one of these fibrous materials may be used singly or two or more may be mixed in any desired proportion. Cotton fibers have been found to be highly satisfactory in the present process and consequently will be used as a specific example in connection with the detailed description of the apparatus and the method of manufacture.

The carding machines are well known in the u textile art'and no detailed description is deemed necessary. Although only four cards are shown in the drawings, any number of cards may be used, depending upon the desired weight or thickness and type of fibrous web being manufactured. 'I'he cards are arranged so that their longitudinal axes are parallel but offset slightly from each other, laterally of the carrier belt II.

Thev carded membranes are delivered from the cards as light, uniform webs and fed by gravity throughprices 9 in the iioor Ill onto a moving carrier belt II, which is slightly undulated by suitable means not shown. This carrier belt is slightly wider than the width of the deposited membranes and may have cooperating flanges for guiding the oncoming membranes onto the traveling support. As the membranes pass through the orifices of the floor, they are shielded from any undesirable external influences, such as strong air currents, by protecting side walls or plates I2 and I3. The carrier beltI I is supported at the opposite ends thereof by the rolls I4' and I5, which are driven by suitable driving means not shown.- The speed of the belt is synchronized the carding operation. and caused to e'xtend in a number of differentdirections, generally nonparallel. This displacement of the fibers is generally normal to the surface of the membranes and, as two or more membranes are brought together, the up-ended fibers of each membrane readily blend together bydef'lnite interengagement or interweaving 1n a. multiplicity of planes.

This action is called aerodynamic weaving.

'Ihe interlocked web is then passed between the rolls Il, I8 and backand forth between the series of rolls 20, which are arranged at successively lower levels. These -rolls do not exert any appreciable pressure on the web and are preferably all driven at the same peripheral speed as the mov.

ing web in order to avoid any tension on the web. I'he back and forth or alternate bending of the web by the rolls 20 serves to alternately lengthen and contract opposite sides of the web, and thisl action further aids in interlocking together the fibers of the successively applied membranes. The

result of the various steps is a firm, homogeneous interlocking structure which is non-lamellar in final appearance and with the individual fibers ,extending in a multiplicity of different directions and disposed in a multiplicity of different planes.

The web I is still light and uncompacted as it leaves the rollsl 20 and passes down around the adjustable roll 2| to a zone where the abrasive grainsare applied to the web and included internally thereof. The abrasive particlespass from the hopper 22 through an adjustable feed gate 23 and over a distributing roll 24 and are deposited by gravity on and into the open structure of the web I: 'Ihe extent of pentration of the abrasive granules into the web may be varied to any desired extent by changing the angle vof the moving web with respect to the falling stream of grain 25. This is readily accomplished by moving the position of the adjustable roll 2| along the path indicated by the curved arrow 26.Y By such adjustment, the web may be moved horizontally and ai an angle of 90 degrees with respect vto the falling stream of grain, or at an oblique angle with respect thereto. The greatest depth of penetration of the grain into the web structure 'will be obtained when the web is moved horizontally and a lesser degree of penetration obtained as the is decreased. The abrasive particles readily penetrate into the intersticesof the web and the with the rate of feed of the membranes in order y to prevent any pull on the membranes during their deposition.

As the fibrous membranes pass down through fibers, due to its open, unconsolidated structure,

and with appreciable improvementfto the interlocking non-lamellar properties of the fibrous web.

^ Thel abrasive-included web is then passed between the rolls 21 and28, where'n'lis consolidated to a desired density and an adhesive binder applied-in sufficient amount to cement the web.l The adhesive roll 28 revolves in a liquid adhesive 29 contained in the pan 30, and upon each revolution, transfers a desired uniform quantity of adhesive into the web. The quantity of adhesive Since is regulated. by the adjustable scraper bar il,

which limits the thickness of the adhesive -layer carried by the roll 28. Tnesetwo rolls are preferably driven at substantially the same speed as theweb passing -therebetween and are provided 5 .with a surface covering of resilient adsorption material. l l

An adjustable baille or shield 32 is provided to cover the front portion of .the adhesive pan 30 and prevent any grain from falling through the l cb and' into the adhesive; After leaving the adhesive-applying device, the consolidated fibrous abrasive web is passedto a .suitable drying or curing chamber, wherelt is l supported by any suitable means, such as by the l rolls 50, until the adhesive binderis fully set or matured. The web is then removed from the'. drying rack and given any additional treatment,

which may be required'and finally cut up into 5 sheets, belts, discs and other abrasive articles of 2n interstices of the fibrous web'where they become 25 securely entrapped and the air is completely dissipated after being completely filtered of all abrasive particles. Necessarily the airvoated abrasive particles 4are controlled both as to .velocity and direction and no distortion of the web occurs. 30,

The adhesive applying rolls illustrated in Figure 1 are also shown in somewhat greater detail. In

this'apparatus the preformed web I is passed from the rolls of Figure 1 directly to an abrasive applying zone.. The abrasive grain isfed 3 6 from a. grain hopper 34, through an adjustable feedgate 35, over a revolving feed roll 3B and throughan inclined chamber 31 into a stream of air issuing. from the air nozzle generally indicated by the reference numeral 38. This stream of air, indicated bythe arrows, projects the abrasive particles ,into the fibrous web and as'the air stream flows therethrough the abrasive material is filtered out of the air stream and deposited within the interstices of the web. The air stream continues on through the open structure web and is dissipated through the space between the shield member 33 and the upper roll 21.

The air nozzle 3l compriseszan inlet primary air supply duct 39, a distributing duct Il, regu- 5 lating means 4| anda distributor orifice I2 for equalizing the airllow within the nozzle. The plate shield and the outlet end of the grain feed chamber 31 'a're adapted to form-a suitable hito the fibrous web. The zone Vof inclusion or Y point where the-airstreamsmkesthewebisiust forwardnfmenipoftnemnszmt. 'rnusastne grain enters the openiihrouswebaliquid adhesive binder 2! is applied sequentially therethrough 60 and the web is consolidated byhthe rolls 21, 12|, The web containing included abrasive and'an adhesivehinderisthenupwardlyfromlhe roll 21 tothe dryilx'rntkll lliownkillgure 1.

'im spparms'ofrlsme :is Impar-w um es' illustratedby Flzllrezandderihed'in connec- `vided an additional niinfeed and VInarderthatgranularrn-powderednnterlalamay beslmultaneouslyoppliedintothewebfromboth 70` asumen n graphite. and the like. can be applied to the op-- posite 'side of the web by the second unit. The subscript. a placed after various of the numbered parts of Figure 3Arepresents parts of the mechanism which are substantially the same as or du plicates of those .parts which are similarly numbered without the subscript a.

The depth of penetration of the abrasive and other powdered materials, applied by the apparatus shown in Figures 2 and 3, can be readily adjustedto any desireddegree by directional control of the air, and pressure control in the nozzle.

Thus the material mayV be applied internally of the web' ln'such amannerthat there is a maxif mum amount of material at opposite surfaces of the web and progressively decreasingtoward the center ofthe web. Or by proper adjustment of the air pressure and grain feedthe abrasive ma-` terial can be deposited substantially uniformly any conventional adhesive applying means, such as the-adhesive roll 28, coacting pressure roll 21 and pan 30 of Figure 1 of the drawings.V A- layer of abraslvegrains may be applied to the adhesive coating by gravitational means, in which a given quantity of grain is uniformly distributed fromV a suitable grain hopper similar to gland permitted to fall thereon. Or, ii` desired, any of the more recently developed electrical and mechanf ical methods of grain deposition and orientation may be utilized. For a more detailed description -ent No. 2,187,624, issued January 14,; 1940, to Romie L. Melton, RaymoncLC. Benner and 'HenryA P. Kirchner.` Suitablemechanical apparatus for-` the orientation and. deposition of abrasive'grains is described in Patent No. 2,141,658, lissued December 27, 1938. This surfacecoating of4 abrasive grain may be applied at "any time Abefore or after partial or completedrying or curing of the included abrasive web. The conventional sizing. coating of adhesive may be applied over the dellosited layer of abrasive grains. 'In' certain in'- stances it is desirable to apply a sizing coating of f adhesive or filler to one or both surfaces of the fibrous web to impart specific properties thereto.

' nozzle for directing the abrasive ladenairstream 55 Any-of the abrasive material Ain common use may be employed in practicing my invention. Such materials include silicon carbide, fused aluv minum oxide, flint, emery, rouge and substances. The size of the abrasive may vary from the nestpolishing or bumng lpowders .to the largest grains now used in thev manufactureofsandpaper. *Y Hgure4isagreatlyenlargedvertica1 crosssection 'cfa fragment of an included abrasive iibrouswebmadeaccordingtoprocees ofthepr" entlinvention. The individual bers of the levenl membranes have been interlocked to :form l. non-lamellar webvstructure and the abrasive srlnuleoll have been internally' of the ilhrolls web. Due to the'illtcring actionot` the nbrous' web. during the application of the Mannheim the number' 0f of the tlhlomyebthanfnenthc bottom; thoalso securely attached by the interlocked bers,

which with the aid of the adhesive binder anv chors them in such position that the upper cutting edges are free for grinding and polishing operations. i

Figure 5 is a similarly enlarged section of an included abrasive fibrous web in which the grains -55 are so distributed that there is a maximum amount of abrasive grain at both surfaces of the web, with the amount of grain progressively diminishing to a minimum toward the center of the iibrous web.

The physical and abrading properties of the included abrasive webs can bealtered to any desired degree by variations-'in the quantity and character of the adhesive binder' agent. The particular adhesive therefor depends upon the specific requirements of the final abrasive product. Latex has been found to be particularly effective as a binder in forming articles of the present invention since itis resistant to Water and is also resilient and fiexible. Other adhesives, however, which may be used instead of, or along with, latex include liquid animal glue, a waterproof resilbility and strength to 2,339,462' wards thel bottom. The granules 55 are firmly of sharp abrasive grains at the grinding surface. Obviously the rate of breakdown of the brous membrane can be regulated and controlled to any desired degree by changes in thev character and quantity of the embrittling agent and the degree of penetration into the individual bers.

Included abrasive articles can be produced in which the outer surface; containing the maximum quantity of abrasive grain', isofA a brittle character-and the opposite side is of a fiexible character. Thus one surface 0f the article funetions most efficiently as an-abrading device, while the opposite surface Vprovides the necessary ilexipermit use as a grinding belt, disc andthe like.' Abrasive materials of such character may be produced by applying an embrittling impregnant to 'onesi'deof the web and applying 4a fiexibilizing impregnantto the opposite side.

Many advantages accrue from practice of theI present invention.` For example, as is readily; apparent from the description, the present invention readily lends itself to the creation of abrasive ient binder such as a synthetic or naturalrubber l binder or the like, va resinous adhesive in liquid or powdered form, sodium silicate andthe like.

One of the important advantages of the invention is that an abrasive article made in accordance with the invention has a resiliency and ilexibility which it is impractical to obtain with either paper or clothf 'Ihe arrangement of fibers in the base material aided by the latex or other adhesive therein, inherently provides a resilient cushioning which insures that, when the abrasive article `is applied to the'surface of the work, each abra'- sive particle will successively contact with the work, the base material yielding so that such contact will be obtained. This property is still further enhanced by proper addition of suitable plasticizers, iiexibilizers and the like within the web. Moreover, it has been found that when using the present base material it is possibleto use an abrasive which is much coarser and therefore faster cutting to obtain a iinish which i. as finev or smooth as that obtained by a much finer and thereforemuch slower cutting abrasive when the ,latter is backed by paper or cloth. This is a. very definite advantage, particularly in the lfinish and longer life for the abrasive particles.

Alternatively, very brittle .characteristics can be imparted to an included abrasive web by the use' of aresinous adhesive, which/cures to a brittle stage. When the fibers are impregnated with a. liquid phenolic resin such as, that .sold under quite brittle and as the surface grains become dulled and break away the exposed embrittled bers alsoqbreak awayand present a yfresh'layei' :wood sanding operations where fine abrasives clog 'the trade name "Durite 8,-2143," they becomey thefface of a backing ied and practiced within the articles; of specific properties in definite consuch properties to other parts of the web where they are unnecessary or even undesirable.

x Furthermore, the present invention provides an abrasive article which obviates the need for a separate backing or other form of lamination, eliminating the weakness ofhaving apluralityof layers which are liable to split apart during use. The base material is a strong, interwo s r ture, especially when internally re-1vfm\ binding materials or like strengthening agents, but at the same time has interstices which serve to anchor the abrasive particles much better than can b e done when they are superimposed upon and are entirely above the surface. Thus the particles are held in place 'or anchored by what may be termeda double ani large portion of the base material itself.

The invention having vbeen fully described and lexplained in its preferred embodiments, it is to be understood that the invention may be embodscop'e of the appended claims.

I claim: A

1. Apparatus for the manufacture of an abra.- sive web having a b ase structure of loosely interwoven bers with interstices therebetween comprising means for forming such an` unlaminated, fibrous web, means forconducting said web into an abrasive grain-applying zone, an air chamber .positioned with its orifice 'facing the weby said orifice shaped to extend substantially transversely of the web, means for maintaining a controlled air pressure in saidchamber above atmospheric pressure for inducing a stream of air against the face and into .the intersticeaof said web, means for introducing abrasive grain into said air stream, means for applying adhesive to the web and for consolidating the same.

' 2.,Apparatus for the manufacture of an abrasive web raving a base structure of loosely interwoven bers withinterstices therebetween comprising means for forming such an unlaminated, fibrous web, means for conducting said web into an 'abrasive grain-applying zone, means for dlrecting a controlled stream of air against the face and into the interstices of said loosely woven web,

means for introducing abrasive grain into'said air stream whereby the force ofthe air stream projects said abrasive graininto the interstices of the web structure, a secondj means positioned on the opposite side ofthe travelling web for directing a controlled stream of air against thev opposite face and into the interstices of said' loosely woven web, means for introducing abra; sive grain and other comminuted materials into said second air stream whereby the air stream projects said materials into the interstices of the web structure, means for applying adhesive to the web and for consolidating the same.

3. The method of manufacturing abrasive articleswhich comprises first forming a loosely woven, open unconsolidated webvof considerable depth from a plurality of thin, carded, sheer fibrous membranes, agitating4 the fibersof said -membranes to bring the fibers of each sheer membrane into interlocking position with the fibers of adjoining membranes, thereafter introducing abrasive grains into the 'interstices beltherebetween comprising means' for forming such an Lunlaminated, fibrous web of considerable depth, means for conducting said fibrous structure into an abrasive grain-applying zone, means for directing a controlled stream of air against the face and'into the interstices of said unconsolidated, loosely woven web, means for intro-` ducing abrasive grains into said air stream whereby the force of the air stream projects said abrasive grains into the interstices of the-web structure-to a considerable depth, means for applying adhesive 'and consolidating the web to a tween the fibersof said loosely woven, open and` unconsolidated web structure, applying a suitable adhesive binder and consolidating the open ing abrasive grains onto the upper surface of the said loosely woven, open, unconsolidated web structure whereby the abrasive grains penetrate into the interstices between the fibers and enter the structure of the web to a considerable depth, applyingra suitable adhesive binder, and consolidating the open, fibrous structure to anchor the included abrasive grains by the closely surrounding fibers andv adhesive, and thereby reducing the web to a relatively thin, strong, abrasive-included sheet.

5.' The method of manufacturing abrasive articles which comprises first forming a loosely strong abrasive-included sheet.

7. Apparatus for the manufacture of an abrasive web having a open, unconsolidated base structure of-loosely interwoven fibers with interstices therebetween comprising means for forming such an unlaminatedfibrous web of considerable depth, means for conducting said web through an abrasive-applying zone, means for feeding a stream of abrasive grains by gravity onto the upper Asurface of said web, adjustable means for regulating the direction of travel of the web into the pathway of the falling abrasive grain whereby the degree and amount of the penetration of the grain internally of the web structure is controlled by the angle of striking 4of the grain into the interstices of the web, means for applying adhesive to the abrasive-laden web and for consolidating the web to a relatively thin, strong, abrasive-included sheet.'

8. Apparatus for the manufacture of' an abra- .,sive web having a open, unconsolidated base structure of loosely woven fibers with interstices therebetween comprising means for formingsuch a fibrous web of considerable depth,'means for conducting saidweb into an abrasive grain-applying zone, means forintroducing abrasive grain 'into the interstices of said fibrous web to a considerable depth, means positioned immediately thereafter for applying adhesive to the abrasiveladen web and for consolidating the web vto a relatively thin, strong, abrasive-included sheet.

9. The method of manufacturing abrasive articles which comprises lrst forming a loosely l woven, open, unconsolidated web of considerable woven, open, unconsolidated web of considerable depth from ,a plurality of thin, carded, sheer fibrous membranes, agitating the fibers of said membranes to bring the fibers of each sheer membrane into interlocking position with the fibers of adjoining membranesfeeding abrasive grains by gravity into the interstices of the said loosely woven, open, unconsolidated web structure to a considerable depth, regulating the direction of travel of the web structure into the pathway of the falling abrasive whereby the degree and amount of the penetration of the grains internally of the web structure is controlled, applying a suitable adhesive binder, -and consolidatingthe open, fibrous structure to an- 'chor therincluded abrasive grains by the closely surrounding fibers and adhesive, and thereby reducing the web to a relatively thin, strong abrasive-included sheet..l i

6. Apparatus for the manufacture of an abrasive web having a open, unconsolidated base structure of loosely woven fibers with interstices depth from a plurality of thin, carded, sheer fibrous membranes, agitating the fibers of said membranes to bring the fibers of each sheer membrane into interlocking position with the l fibers of adjoining membranes, thereafter projecting abrasive grain by means of an air streaml into the interstices between the fibers of said loosely woven, open and unconsolidated web structure, applying a suitable adhesive .binder and consolidating the open fibrous structure to" anchor the included abrasive grains by. the closely surrounding fibers and adhesive, and thereby reducing'the web to a relatively thin, strong, abra-` sive-included sheet.

10. The method of manufacturing abrasiveA vmembrane into interlocking position with the fibers of adjoining membranes, `thereafter projecting abrasive grain by means of air streams directed at both faces of theweb into the interstices between the bers of said loosely woven;

open and unconsolidated web structure, applying' a suitable adhesive binder and consolidating the open fibrous structure to anchor the included abrasive grains by the closely surrounding fibers depth from av plurality of thin,- carded, sheerv brous membranes, agitating the bers of said membranes to bring the bers of eachsheer membrane into interlocking position with the bers of adjoining membranes, thereafter directing a stream of airagainst the fame of said unconsolidated web, introducing abrasive grain into the air'stream whereby the abrasive grain is carried by said air stream into the interstices be. tween tlie bers of said loosely woven, open and unconsolidatedv web structure, applying a suitable adhesive binder and consolidating the open iibrous structure to 'anchor the included abrasive grains by the closely surrounding bers and adhesive, and thereby reducing the web to a -rel-a'- tively thin," strong, abrasive-included sheet.

12. The method of manufacturing abrasive articles which comprises rst forming a loosely woven, open, unconsolidated web of considerable 'depth from a plurality of thin, carded, sheer fibrous membranes, agitating the bers of said membranes to bring the bers of each sheer membrane into interlocking position with the fibers of adjoining membranes, thereafter projecting abrasive grains by means of an air stream into the interstices between the bers of said loosely Woven, open and unconsolidated web structure, projecting a powdered anti-'friction material by means o f an air stream directed towards the opposite face of said web into a portion of the unconsolidated web structure, applying a suitable adhesive binder and |consolidating the open brous structure to. anchor the included abrasive grains by the closely surrounding bers and adhesive, and thereby reducing the web to a rela- 20'tive1ythin, strong., abrasiveinc1uded sheet.

EDWARD HURST. 

